GEOLOGY

Detailed explanation-1: -A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors.

Detailed explanation-2: -What determines how destructive a tsunami will be near the origin and at a distant shore? Tsunamis arrive at a coastline as a series of successive crests (high water levels) and troughs (low water levels)-usually occurring 10 to 45 minutes apart.

Detailed explanation-3: -On its arrival on shore, the height of the tsunami varied greatly, depending on its distance and direction from the epicentre and other factors such as the local bathymetry. Reports have the height ranging form 2-3 m at the African coast (Kenya) up to 10-15 m at Sumatra, the region closest to the epicentre.